Following a suggestion from Make: I played a bit with this unit of modular origami. The basic unit looks like:

Basic sonobe unit

It can be then assembled by 3, 12, 30 or more (Make: article explains what the obtained form is):

Three units

Twelve units

Thirteen units

The next week, another article introduced a few more complex volumes, out of which I reproduced a Menger sponge of first order (72 sonobe units, the second order is 1152 ones):

Menger sponge of first order

Time to study the math behind it, making more original volumes, or using different units.